REF-1309 · Knapik et al., 2006 · Military Medicine · Paper · PubMed

Should someone low-fit get fitter before starting a demanding programme?

In Army recruits, those who trained until they passed an entry test finished basic training far more often (83% vs 59% of men). Observational, military.

Main caveat: Non-random comparison. Allocation to FAP or straight into BCT was not random and its reason is not given.
limited evidenceMeasured on non-athletes and recreational people

From October 1999 to May 2004, recruits arriving for US Army basic combat training (BCT) took an entry-level fitness test. Those who failed it entered the Fitness Assessment Program (FAP), where they trained until they passed and then started BCT — the preconditioned (PC) group, 64 men and 94 women.

Some recruits who failed the test entered BCT without the FAP — the no-preconditioning (NPC) group, 32 men and 73 women. Recruits who passed went straight in (no need of preconditioning, NNPC: 1078 men, 731 women). Completion of the 9-week cycle was 59%, 83% and 87% for NPC, PC and NNPC men and 52%, 69% and 78% for women (both p < 0.01).

Against fit recruits, injury risk was 1.5 (95% CI 1.0-2.2) times higher in PC men and 1.7 (1.0-3.1) in NPC men; 1.2 (0.9-1.6) in PC women and 1.5 (1.1-2.1) in NPC women. The authors conclude that low-fit recruits who preconditioned had reduced attrition and tended to have lower injury risk than similarly low-fit recruits who did not.

Our reading: a large attrition difference (about 24 points in men, 95% CI roughly 5 to 43, and 17 in women, roughly 2 to 32; our arithmetic from the abstract's percentages and group sizes) in a non-random comparison that cannot exclude selection, and an injury difference that the confidence intervals do not separate.

It is the only evaluation in the base of a gate defined by a test rather than by weeks.

Protocol

Design: programme evaluation of routine Army data (company-level database and medical records; the abstract does not say whether it was retrospective); groups defined by the entry test and by whether a low-fit recruit went through the FAP. Why some low-fit recruits entered BCT without the FAP is not given in the abstract.
Who: n = 2072 recruits — PC 158 (64 men, 94 women), NPC 105 (32 men, 73 women), NNPC 1809 (1078 men, 731 women).
The gate: an entry-level physical fitness test at the reception station; FAP recruits "physically trained until they passed the test". The test's events and the time spent in the FAP are not in the abstract.
Outcomes: completion of the 9-week BCT cycle; Army Physical Fitness Test (APFT) scores at week 7 and final pass after retakes (company-level database); injuries from medical records.
Analysis: proportions compared across the three groups; injury risk ratios with 95% CIs against the fit group.
Funding and interests: not given in the abstract; the first affiliation is the U.S. Army Center for Health Promotion and Preventive Medicine (a military public-health body, not a commercial funder).

Key Results

OutcomeLow fit, straight into BCT (NPC)Low fit, preconditioned (PC)Fit (NNPC)p
Completed 9-week BCT, men59%83%87%< 0.01
Completed 9-week BCT, women52%69%78%< 0.01
Took the week-7 APFT63%84%86%—
Passed the final APFT after all retakes, men88%92%98%< 0.01
Passed the final APFT after all retakes, women89%92%97%< 0.01
Injury risk vs fit recruits, men (95% CI)1.7 (1.0-3.1)1.5 (1.0-2.2)1 (reference)—
Injury risk vs fit recruits, women (95% CI)1.5 (1.1-2.1)1.2 (0.9-1.6)1 (reference)—
Attrition, preconditioned vs not (our arithmetic): men 83% vs 59%, a 24-point difference (95% CI about 5 to 43; 64 vs 32 recruits); women 69% vs 52%, 17 points (about 2 to 32; 94 vs 73).
Injury: PC and NPC were each compared with fit recruits, not with each other; their intervals overlap widely, which is why the authors say PC recruits "tended" to have lower injury risk. Both low-fit groups carried more injury risk than fit recruits.
Fitness at the end: among those who stayed, most passed the final APFT in every group (88-98%).

Mechanisms

Measured: completion of training, end-of-training fitness test results and medical-record injuries by group.
Authors' interpretation: preconditioning low-fit recruits before BCT reduced attrition and tended to lower injury risk.
Inference: selection is built into the groups. The PC group is defined as recruits who trained in the FAP and passed the test; anyone who entered the FAP and never passed is not in it. Part of the attrition advantage may be that PC recruits had already shown they could improve and persist.
Inference: the reason some low-fit recruits were sent straight in is not given; if it was administrative (timing, waivers), the NPC group may differ in other ways.
Inference: a gate defined by passing a test, rather than by a fixed number of weeks, lets each person take the time they need — the logic of "start the specific block when the base is repeatable"; this study supports the attrition side of that logic in recruits only.

Practical Application

Should someone low-fit get fitter before starting a demanding programme? In Army recruits, those who trained until they passed an entry test finished basic training far more often (83% vs 59% of men). Observational, military.
If a gate is used, define it by a capacity the athlete demonstrates, not by a date (B, transfer from recruits; the gate itself is practice for athletes): e.g. for a running beginner, continuous easy running of 20-30 min without symptoms before structured faster work — the base's own practice in SYNTH-75, not a threshold this study tested.
Do not present the gate as injury prevention: injury risk in preconditioned recruits was not shown to differ from that of low-fit recruits sent straight in, and both stayed above fit recruits (1.2-1.7 times).
Low fitness itself is a risk marker for injury and for not finishing a programme (B, recruits); in civilian novices, no running history went with injury in two Dutch cohorts (REF-1313, REF-1312) but not in 930 Danish novices (REF-926), and injury was the main reason novices quit (REF-1311).
Scale: basic training is a fixed, high-volume, mandated load; an amateur's plan can bend to the athlete instead (inference). The tolerance-first trials in civilian novice runners found no fewer injuries (REF-1307, REF-925).

Limitations

Non-random comparison. Allocation to FAP or straight into BCT was not random and its reason is not given; the preconditioned group includes only those who passed the test, a survivor selection.
Read from the abstract. The fitness test, the time spent preconditioning, adjustment for confounders (age, body mass, initial score) and injury definitions are not available.
Small low-fit groups. 32 NPC men and 64 PC men; the attrition differences have wide intervals (our arithmetic).
Outcome. Completion of military training depends on administrative decisions as well as fitness and injury.
Population. US Army recruits, 1999-2004, in a mandated programme; TRANSFER to civilian athletes is inference.
Funding and interests: not in the abstract; authors from the U.S. Army Center for Health Promotion and Preventive Medicine.
How this entry was checked and changed
Why this level

(from the abstract) — an observational cohort over 200 sits in the rubric's B+ band; held at B because the contrast that matters (low-fit recruits with vs without preconditioning, 158 vs 105) is non-random and the abstract does not say why some low-fit recruits went straight into training, the preconditioned group by definition includes only those who passed the test, completion of training is partly an administrative outcome, and only the abstract was read (the full text is not open)